35 ILCS 200/10-25
If the construction of a single family dwelling is completed after December 29, 1986 or the construction of a single family townhome or condominium unit is completed after the effective date of this amendatory Act of 1994, and that dwelling, townhome, or condominium unit is not occupied as a dwelling but is used as a display or demonstration model home, townhome or condominium unit for prospective buyers of the dwelling or of similar homes, townhomes, or condominium units to be built on other property, the assessed value of the property on which the dwelling, townhome, or condominium was constructed shall be the same as the assessed value of the property prior to construction and prior to any change in the zoning classification of the property prior to construction of the dwelling, townhome or condominium unit. The application of this Section shall not be affected if the display or demonstration model home, townhome or condominium unit contains home furnishings, appliances, offices, and office equipment to further sales activities. This Section shall not be applicable if the dwelling, townhome, or condominium unit is occupied as a dwelling or the property on which the dwelling, townhome, or condominium unit is situated is sold or leased for use other than as a display or demonstration model home, townhome, or condominium unit. No property shall be eligible for calculation of its assessed value under this Section for more than a 10-year period. If the dwelling, townhome, or condominium unit becomes ineligible for the alternate valuation, the owner shall within 60 days file with the chief county assessment officer a certificate giving notice of such ineligibility.
For the purposes of this Section, no corporation, individual, sole proprietor or partnership may have more than a total of 3 model homes, townhomes, or condominium units at the same time within a 3 mile radius. The center point of each radius shall be the display or demonstration model that has been used as such for the longest period of time. The person liable for taxes on property eligible for assessment as provided in this Section shall file a verified application with the chief county assessment officer on or before (i) April 30 of each assessment year for which that assessment is desired in counties with a population of 3,000,000 or more and (ii) December 31 of each assessment year for which that assessment is desired in all other counties. Failure to make a timely filing in any assessment year constitutes a waiver of the right to benefit for that assessment year.
35 ILCS 200/10-25